On board the artificial satellites in recent years is an electric power source of solar battery array composed of a plurality of solar cells connected in series with each other. Most electric power needed in the artificial satellite is usually generated in the solar cell array. The electric power to be consumed in the artificial satellite has a tendency to become higher every year and correspondingly the satellite demands the high-power generators which are able to create the generated output above 100V. In existing situations, the artificial satellites become increasingly great in scale or dimension as seen in spacecrafts or spaceships and space stations and, as size increases, the solar cell modules or arrays need to be higher in electric potential.
The electric discharge or arc is normally caused by any potential difference which might occur between an insulator such as a cover glass or the like and a conductor such as spacecraft body and so on because of the interaction with the surrounding environment including substream, plasma and so on.
The single-discharge on the solar battery array, called primary arc, gives rise to not only degradation of the solar cells but malfunction of the onboard instruments. The discharge energy in the primary arc is traced to the energy of electric charges built up between the spacecraft body and the cover glass. A further difficult problem resides in a phenomenon that the discharge energy just after the primary arc on the solar battery array would cause short-circuit between the solar cells across which high potential difference exists. This short-circuiting phenomenon is called the secondary arc or sustained arc or discharge (SA). As the short-circuit current occurring during the sustained arc is continued getting fed from the solar battery array in generation, the output of the circuit would be lost in between the sustained arc.
Now referring to FIG. 9, there is shown a conventional solar battery array 3 carried on the artificial satellite 4. The prior solar battery array 3 has a series circuit 2 in which solar cells 1 are connected in series with one another and a gap 8 exists between a positive-side line 5 and a negative-side line 6. Inside the artificial satellite 4, there are electric circuits 13 to energize various instruments onboard the satellite 4. With the solar battery array 3 constructed as stated earlier, arrows indicate a path for electric current which could flow through after a sustained discharge or arc (SA) has occurred at the gap 8. The sustained discharge or arc (SA) having occurred in the solar battery array 3 accompanies intense light and overheating which, if worst comes to worst, could do fatal damage in which the solar cells would lose forever the ability of generating electricity.
The arcs or discharges occurring on the solar battery array 3 onboard the artificial satellite 4 are classified into four categories using their waveforms: a primary arc (PA) displaying a waveform as shown in FIG. 10 (A), and secondary arcs or sustained arcs (SA) having waveforms as in FIGS. 10 (B), (C), and (D). Moreover, the secondary arcs include a non-sustained arc (NSA) as in FIG. 10 (B), a temporary sustained arc (TSA) as in FIG. 10 (C) and a permanent sustained arc (PSA) as in FIG. 10 (D). The non-sustained arc (NSA) refers to a discharge in which the discharge current continues flowing only during the primary arc (PA). With the temporary sustained arc (TSA), the discharge current remains flowing after the primary arc current has ceased flowing, but soon disappears. The permanent sustained arc (PSA), unlike the temporary sustained arc (TSA), refers to a discharge where the discharge current continues flowing forever. Sign Ist in FIG. 10 shows an electric current flowing at the time of short circuiting. Conditions the sustained arc (SA) occurs vary depending on a gap length lying between the solar cells 1, a generated potential (Vst), the current (Ist) flowing through the solar cells 1, magnitude of the primary arc (PA) and so on. The existing technique to control or inhibit the sustained arc is to fill in all the gaps 8 with room-temperature-curing (RTV) silicone sealant to prevent the occurrence of electric potential difference.
Meanwhile, there has been conventionally known a power system onboard artificial satellite having a power supply having solar battery or solar cell array. The prior power system onboard artificial satellites, as disclosed in, for example patent document 1 enumerated later, has solar cells, and super-capacitors which are used to store the solar-generated energy and then power any loads as solar-generated energy are reduced. The super-capacitors are connected in parallel with Zener diodes to keep an upper limit for an output voltage to the loads. The solar cells charge the super-capacitors while powering the loads through the terminals. As the solar cells cease generating electricity after having gone into the shade, the super-capacitors start to discharge the stored solar-generated energy.
Moreover, the patent document 2 listed later discloses a bus voltage regulator used in the power source for the cosmonautic vehicle such as the artificial satellite and so on. The prior bus voltage regulator has a voltage regulator monitoring the solar-generated energy that is not needed immediately, based on a voltage value on a buss line through which the solar-generated power is applied to loads of instruments onboard the artificial satellite, and a circuit to shunt the solar-generated power in response to the voltage regulator. The voltage regulator further includes a shunt resistance connected in parallel with a load to regulate the bus voltage, and a switch to break the shunt-circuit to operate the solar cells with high efficiency.